Device-to-device (English: Device-to-Device, D2D for short) communication refers to direct communication between user equipment. A device-to-device proximity service (English: Device to Device Proximity Service, D2D ProSe for short) has become a research subject in a Rel.12 system in a Long Term Evolution (English: Long Term Evolution, LTE for short) system in the 3rd Generation Partnership Project (English: 3rd Generation Partnership Project, 3GPP for short), and D2D communication is supported since the Rel.12 system.
In a D2D direct-connection communication scenario, multiple users form a user group (Group) or a user cluster (Cluster). Within a group or cluster, multiple users share specific time and frequency resources. In a D2D ProSe scenario, multiple user groups may coexist. In this case, to avoid interference between different user equipment or between different user groups, resource allocation needs to be coordinated between different user groups.
In a general commercial communications system, resources used by the communications system are planned in advance, and are free from a temporary contention problem. For example, in a WiFi network, a user may manually select a frequency channel used by the network, or may use an automatic selection manner in which the system performs energy detection and selects a frequency channel with relatively low interference. Once a frequency channel is selected, the user uses a contention access manner.
An existing resource allocation technology cannot be directly applied to the D2D direct-connection communication scenario, specifically, for example, a broadcast communication scenario without control from a central node in D2D direct-connection communication design, because user equipment with a higher access channel priority exists in the broadcast communication scenario of D2D direct-connection communication. If the existing resource allocation technology such as a CSMA access method is applied, user equipment have a same access priority, and therefore, high-privilege user equipment or user equipment of a higher service priority cannot be given access precedence.
The existing resource allocation technology does not allow flexible allocation and contention in a time domain, and cannot be directly applied to an LTE-based D2D direct-connection communications system.